Extensive molecular-biochemical studies of normal and cancerous cells have revealed that abnormality in the signal transmission involved in the growth and division of cells causes cancer, and also that proteins produced by the expression of oncogenic genes regulate the growth and division of cells. Namely, it has been reported that growth factors, growth factor receptors, cellular tyrosine and serine/threonine kinases and phosphatases, Ras proteins, adaptor proteins, transcription factors, and the like take part in the intracellular signal transmission and play crucial roles in cell proliferation (see, for example, Alexander, L. (1994) Eur. J. Biochem. 226, 1-13; Hahn W. C. and Weinberg R. A. (2002) Nat Rev Cancer 2(5):331-41; Blume-Jensen P. and Hunter T. (2001) Nature 411(6835):355-65).
For example, intracellular signal transmission through Ras occurs when a signal transmitting substance binds to a growth factor receptor, such as, for example, ErbB2, which causes phosphorylation of tyrosine on the receptors. The receptors phosphorylate tyrosine 317 in Shc (Src homology and collagen protein), which in turn is recognized by Grb2-(Growth factor receptor-binding protein-2) SOS complexes. As a result, SOS is translocated to the cellular membrane which appears to facilitate its ability to activate Ras (see, for example, Batzer, A. G., et al. (1994) Mol Cell Biol 14(8):5192-201; Buday, L. and J. Downward (1993) Cell 73: 611-620; Feig, L. A. (1994) Curr Opin Cell Biol 6(2): 204-11; Karin, M. and T. Hunter (1995) Curr Biol 5(7): 747-57; Meyer, S., et al. (1994) Mol Cell Biol 14(5): 3253-62; Seger, R. and E. G. Krebs (1995) Faseb J9(9): 726-35; Segatto, O., et al. (1993) Oncogene 8(8): 2105-12; Sutherland, R. L., C. K. Watts, and E. A. Musgrove (1993) J Steroid Biochem Mol Biol 47(1-6): 99-106) leading to stimulation of DNA synthesis, cell proliferation and differentiation.
Furthermore, several studies using microinjected antibodies to Shc, Shc antisense, and various Shc dominant-negative constructs have shown the dependence on a functional Shc for signaling through the EGF receptor, Her2/Neu, IGF-1 and HGF (see, for example, Nolan, M. K., et al. (1997) Int J Cancer 72(5): 828-3; Xie, Y., K et al. (1995) Oncogene 1995. 10(12): 2409-2413; Gotoh, N., et al. (1995) Oncogene 11(12): 2525-2533; Pelicci, G., et al. (1995) Oncogene 10(8): 1631-8; Sasaoka, T., et al. (1994) J Biol Chem 269(18): 13689-94; Stevenson, L. A., et al. (1999) Cell Growth & Differentiation 10(1): 61-71); and Song, R. X., et al. (2006) Proc Natl Acad Sci USA 101(7):2076-4081). There are three isoforms of Shc: p66, p52 and p46 of 66, 52, and 46 kDa, respectively (see, for example, Songyang, Z., et al. (1993) Cell 72(5): 767-78; Pelicci, G., et al. (1992) Cell 70(1): 93-104; Rozalis-Adcock, M., et al. (1992) Nature 360(6405): 689-92). The p66 Shc isoform contains a unique N-terminal domain (CH2) not found in the p52 or p46 Shc isoforms (Pelicci, G., et al. (1992) Cell 70(1):93-104). In contrast to p52 and p46 Shc, p66 Shc typically does not activate the MAP kinase signaling cascade but rather actually inhibits the ability of growth factors to activate both MAP kinase and c-fos (Migliaccio, E., et al. (1997) Embo J 16(4): 706-16; Pacini, S., et al. (2004) Mol Cell Biol 24:1747-57; Trinei, M., et al. (2002) Oncogene 21:3872-8). Additionally, p66 Shc is an apoptotic sensitizer to oxidative stress (Migliaccio, E. et al. (1999) Nature 402(6759):309-313; Nemoto, S. et al. (2002) Science 295(5564):2450-2452; Orsini, F. et al., (2004) J Biol Chem 279(24):25689-25695; Pacini, S. et al. (2004) Mol Cell Biol 24(4):1747-1757; Purdom, S. et al. (2003) Trends Mol Med 9(5):206-210; and Trinei, M. et al. (2002) Oncogene 21(24):3872-3878). Such stress may be generated by chronic activation of growth-factor pathways, by infiltrating neutrophils and macrophages, and/or by neo-vascularization of hypoxic tumors (Brown, N. S. et al. (2001) Breast Cancer Res 3(5):323-327; Irani, K. et al. (1997) Science 275(5306):1649-1652).
For patients diagnosed with cancer, e.g., gastrointestinal cancer, surgical and medical oncologists currently must balance the minimal likely benefit that might be derived from the aggressive level D2 surgery and toxic chemo-radiation regimen adopted by some as the current standard of care (MacDonald, J. (2001) N. Engl J Med 345:725-730) against the modest risk (approximately 20%) that patients with early stage cancer treated only by level D1 surgical resection will have recurrent disease. Prognostic markers that will identify patients who are likely (and those unlikely) to experience recurrent disease will aid and improve this clinical treatment decision.
Thus, there is an urgent need in the field for better prognostic indicators to guide the vigor and extent of surgical and adjuvant therapies of patients, especially those with early stage cancer.